progrium/buildstep — pull request #128 by CharlieC3 (2014-12-19 21:56:15+00:00)
Title: Updating Java buildpack to latest revision

There are some crucial recent updates to the Java buildpack, some of which are noted in this merged pull request, which allow mvn to be run with custom options and goals:
https://github.com/heroku/heroku-buildpack-java/commit/cced6c6388f9b2ccfe914c84f5dc68e5d244a6a8